From 54cfdb3e95d4f70409a7d3432a42cffc9a232be7 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 27 Mar 2014 11:36:25 +0100 Subject: [PATCH] KVM: emulate: speed up emulated moves We can just blindly move all 16 bytes of ctxt->src's value to ctxt->dst. write_register_operand will take care of writing only the lower bytes. Avoiding a call to memcpy (the compiler optimizes it out) gains about 200 cycles on kvm-unit-tests for register-to-register moves, and makes them about as fast as arithmetic instructions. We could perhaps get a larger speedup by moving all instructions _except_ moves out of x86_emulate_insn, removing opcode_len, and replacing the switch statement with an inlined em_mov. Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_emulate.h | 2 +- arch/x86/kvm/emulate.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h index 0e0151c13b2c..432447370044 100644 --- a/arch/x86/include/asm/kvm_emulate.h +++ b/arch/x86/include/asm/kvm_emulate.h @@ -233,7 +233,7 @@ struct operand { union { unsigned long val; u64 val64; - char valptr[sizeof(unsigned long) + 2]; + char valptr[sizeof(sse128_t)]; sse128_t vec_val; u64 mm_val; void *data; diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index ea56dae3e67c..27f677ef703e 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2990,7 +2990,7 @@ static int em_rdpmc(struct x86_emulate_ctxt *ctxt) static int em_mov(struct x86_emulate_ctxt *ctxt) { - memcpy(ctxt->dst.valptr, ctxt->src.valptr, ctxt->op_bytes); + memcpy(ctxt->dst.valptr, ctxt->src.valptr, sizeof(ctxt->src.valptr)); return X86EMUL_CONTINUE; } -- 2.20.1